Free Simple Circuit Diagram
This is a phone bug circuit. This wireless telephone line spy circuit can be used to transmit the phone conversation to a nearby FM radio. This circuit must connected to a normal phone line. Here is the schematic diagram of the circuit: The first transistor is turned off, if the voltage drops to less than 15v (if the telephone line […]
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This is a power on circuit that works temporarily only when the power is turned on, this LED illuminates for a few seconds, then turns off again. This design is eco-friendly since it consumes only a little power at the beginning of the power connection. Here is the schematic diagram of the circuit: The circuit uses the 47uF capacitor that […]
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This is a voltage multiplier circuit. First circuit is used to double the a square wave (any amplitude). However there is minus about 2v losses in base-emitter of the transistors and the diodes in first circuit. To work, second circuit must fall to nearly 0.4v and rise to at least 5.6v. to prevent short-circuiting and both transistors coming on at […]
Read moreThis is aquiz bell/alarm circuit. This circuit indicate “fastest finger first”. This circuit has one bulb for Quiz master and one for each contestant. The bulb will illuminate when a button is pressed. the cathode of the 9v1 zener sees approx mid-rail voltage. The Quiz Master bulb is also illuminated. Here is the circuit: There is no other bulbs can […]
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